The present invention relates to stiffeners, and in particular, to circuit board stiffener that may be used with an automated test system.
Circuit boards are typically used for connecting a variety of electronic devices together to implement a variety of different functions. Typically, different types of integrated circuits (i.e., “ICs”), passive components, or other devices may be mounted on the surface of the circuit board. Circuit boards further include multiple layers to metal or other conductive material for conducting electric current and carrying electrical signals between the devices. Circuit boards are typically manufactured from fiberglass, and therefore, are typically only semi-rigid structures. The electrical devices and components, as well as the electrical connections between them, can be very sensitive to stress or bending when the circuit board is used in a real world application. Many electronic applications attach stiffeners to circuit boards to protect the circuit boards from various physical shocks, disturbances, impacts, or other types of bending or stress. A stiffener is a rigid piece of material that may be used to reinforce and support the circuit board.
FIG. 1 is an example application of a circuit board stiffener. FIG. 1 illustrates an automated test environment including automated test equipment 101 (“ATE”) coupled to a test head 102. ATE 101 may be any of a variety of automated testers such as, for example, an integrated circuit tester by Teradyne, Inc.®. Testers typically include electronic systems and resources in the main tester body 101. The resources may be coupled to a test head 102, which may include yet more electronic resources and systems. The resources and systems of the tester may be coupled to a circuit board 103 (sometimes referred to in this application as a “load board”) by placing the circuit board in contact with connectors on the test head (not shown). Numerous integrated circuits may be sequentially tested by coupling circuit board 103 to a parts handler 104. Circuit board 103 and parts handler 104 are typically coupled together at a contact point so that one or more integrated circuits in parts handler 104 may be sequentially brought into electrical contact with the circuit board and tested.
Generally, the testing of different integrated circuits requires different circuit boards because the different ICs typically require different tester resources to be properly tested. Thus, in a production environment, circuit boards on a given tester may be interchanged on a regular basis. The process of installing a circuit board on a tester and connecting the handler (sometimes referred to as “docking”) can result in severe stress on the circuit board. Moreover, when the handler is operating, individual ICs may be physically forced against the circuit board by motors, actuators or other mechanisms, which may also result in severe shocks and stresses on the circuit board. Thus, it has become common for circuit boards to be provided with a stiffener to provide structural support.
FIGS. 2A and 2B show an example of a circuit board and stiffener that is used in an ATE environment. FIG. 2A shows a side view of the circuit board and stiffener, and FIG. 2B shows a bottom view. Stiffener 201 typically provides peripheral support to circuit board 202 and defines an opening through the center. Tester resources may be coupled to circuit board electronics using connections (e.g., pogo pins, ribbon cables or other types of connectors) that pass through the opening in the stiffener. Circuit board 202 may be attached to stiffener 201 using screws (not shown), for example. Stiffener 201 typically includes a lower surface 203A for abutting to a test system. A variety of mechanisms may be used that allow a user to attach and detach the stiffener to the test system. The upper surface 203B of stiffener 201 may be attached to circuit board 202. In some applications, a contactor 204 such as a edge connectors, for example, may be used to provide electrical connections between the circuit board and ICs in the handler.
FIG. 3 illustrates another stiffener 301 and circuit board 302. As the complexity of integrated circuits grows, correspondingly more complex testers and circuit boards are required to properly test the ICs. For example, modern digital, analog, or mixed signal ICs may include hundreds of device pins, which may require several hundred separate tester resource connections between the tester and the circuit board. Thus, the circuit boards used to test such devices can be very large, and the stiffeners used to support these circuit boards may also be very large. Stiffener 301 is attached (e.g., by screws) to circuit board 302. Stiffener 301 may be constructed from aluminum or other strong rigid material, and thus may become very heavy as the size of the circuit board grows. Two handles 310A and 310B are attached to the outer sidewall of the stiffener to facilitate handling of the circuit board when it is being attached to or removed from the tester and moved around the production facility. Attachment bars 311A and 311B are included to allow the stiffener to engage an attachment mechanism on the tester. Stiffener 301 further includes transverse beams 320 and 321 to add additional support to the stiffener frame. The periphery and transverse beams of the stiffener define openings 350, 351, and 352. As shown in FIG. 4, tester resources, such as channel cards, may be coupled through the openings using spring actuated pogo pin blocks to bring tester resources into contact with the circuit board electronics.
As mentioned above, as integrated circuits become more complex, the circuit boards and stiffeners (together, “load board”) used to test them become larger. As the circuit boards become larger, the stiffeners used to support them become heavier. If many different ICs are being tested, a user may be required to attach and detach many load boards to an ATE. The excessive weight of the stiffeners can make interchanging load boards burdensome and difficult. Moreover, these large load boards may take up a lot of space for storage. As mentioned above, each IC product may require a corresponding load board. Additionally, multiple copies of the same load board are typically built so that the same IC product can be tested simultaneously on more than one tester. Thus, in a production environment hundreds or even thousands of load boards must be transported between testers and stored while not in use. To add to these problems, each stiffener may be very expensive. Stiffeners for use in an ATE environment may cost hundreds or even thousands of dollars. It would generally be desirable to reduce to weight, cost, and storage burden of contemporary stiffeners.
Thus, there is a need for improved circuit board stiffeners. The present invention solves these and other problems by providing an improved circuit board stiffener that may be used in automated test environments.